Process for the recovery of zinc compounds from zinc-chloride solutions



Patented May 5, 1925.

UNITED STATES PATENT orrice.

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PROCESS FOR THE RECOVERY OF ZINC COMPOUNDS n01! ZII I'C OHLORIbE SOLUTIONS.

Io Drawing.

To all whom it may concern:

Be it known that I, ALEXANDER NATHAN- soHN, acitizen of German residing at 6 Goslarsche Street, Bad many,,have invented certain new and useful Improvement in Process for the Recovery of Zinc Compounds from Zinc-Chloride So- ,lutions, of which the.,foll,owing is a specification.

The object of the present invention is to obtain the zinc values in solutions ofzinc chloride or in mixtures containing zinc or zinc chlorides such as the products known in the tradeas sal-ammoniac slags.

An econoniical method of recovering the zinc values in zinc chloride solutions has long been sought and it is believed the solution of this problem is found in the present invention. It has already been proposed to recipitate solutions of zinc chloride with ordinary lime (calcium hydroxide) but the preci itate obtained by this procedure is filprecipitate of zinc hydroxide in suspension,

carbon dioxide. lBy treatment with the carbon dioxide carbonate of zinc is formed which gives a precipitate which is readily filterable and from which all the chlorine" may be removed by washing with water. The treatment with carbon dioxide should be continued until all of the hydroxides present in the recipitate have been transformed into carbonates, which point may be determined by the disappearance of the basic reaction of the mixture. The precipitate should then be washed with water until all chlorides have been removed and after having been dried or calcined, may then be treated metallurgically to obtain the zinc values therein.

In practice the carbon dioxide used" in this process may be obtained by calcining Application med larch 7, 1924. Serial no. cause.

arzburg, Gercalcium carbonate or by the use of any gases containing carbon dioxide in suitable quantities such as waste combustion gases.

The present process is especially suitable for the treatment of so-called sal-ammoniac slags. then. added so that a suspension of the round slags is formed. To this liquid sufcient lime is added to transform the zinc chloride present into zinc hydroxide and when this transformation is complete, carbon dioxide gas is introduced into the mix-- ture to form zinc carbonate. The precipitate formed is filtered off, is washed andthen may be treated in any suitable manner for the recovery of the zinc values therein.

I am aware that it has already been'proposed to treat zinc chloride solutions with calcium carbonate but this process is very incomplete at ordinary temperatures and even with the assistance of heat is unsatisfactory, whereas the present process will work satisfactorily at ordinary temperatures. Sufiicient lime should be added so that zinc oxychloride is formed. which is then treatedwith carbon dioxide.

A working example of my improved process is as follows A ton of zinc chloride solution containing 90 kilograms of zinc is treated with an equivalent amount of milk of lime containmg" 200 kilograms calcium hydroxide per ton. The end of the reaction may be noted when the filtrate from the mixture is free from zinc and slightly alkaline. Then carbon dioxide from any suitable source is introduced until two thirds of the zinc hydroxide present is saturated with carbonic acid. The end of the reaction may be noted by the fact that the amount of chlorine in the mixture and in the filtrate is identical which shows that the precipitate is free from chlorine.- lhe: precipitate is washed until all traces of chlorine have been removed.

The slags are ground and water isv Having thus fully explained my invensuspension with lime and introducing carsuch zinc roducts with lime in contact with m bon dioxide into the mixture. water, sub ecting the resultant precipitate to 3. The process of recovering zinc values the action of carbon dioxide so as to convert from waste products containing zinc by said precipitate into zinc carbonate and 5 treating said roducts in contact with water washing said zinc carbonate until it is free with lime an subjectin the resultant precifrom chlorine. 15 tate to the action of car, on dioxide. In testimony whereof I hereunto aflix my.

4. The rocess of recovering zinc values signature. from pro ucts containing zincfby treating ALEXANDER NATHANSOHN. 

